The quotation of the week last week had to be that of Harvard professor Daniel E. Lieberman in an opinion piece for the New York Times.

Lieberman, a professor of human evolutionary biology, was among those who publicly defended New York City Mayor Michael Bloomberg’s plan to ban the sale of sugared soft drinks in cups larger than 16 ounces.

And he did so using, of all things, evolution.

Now, we all know that humans have always needed – or evolved to need – carbohydrates for energy. So how could evolution argue for Mayor Bloomberg’s ban on sugar, a pure carbohydrate?

In order to understand both how silly and dangerous this comment is, one must first understand the role evolutionary explanations play in academic life – and in left-wing life generally. The left has always sought single, non-values based explanations for human behavior. It was originally economics. Man is homo economicus, the creature whose behavior can be explained by economics.

Rather than dividing the world between good and evil, the left divided the world in terms of economics. Economic classes, not moral values, explain human behavior. Therefore, to cite a widespread example, poverty, not one’s moral value system, or lack of it, causes crime.

Recently, however, the economic explanation for human behavior has lost some of its appeal. Even many liberal professors and editorial writers have had to grapple with the “surprising” fact that violent crime has declined, not increased, in the current recession.

In the words of “Scientific American,” “Homo economicus is extinct.”

But the biggest reason for the declining popularity of economic man is that science has displaced economics – which is not widely regarded as a science – as the left’s real religion. Increasingly, therefore, something held to be indisputably scientific – evolution – is offered as the left’s explanation for virtually everything.

Evolution explains love, altruism, morality, economic behavior, God, religion, intelligence. Indeed, it explains everything but music. For some reason, the evolutionists have not come up with an evolution-based explanation for why human beings react so powerfully to music. But surely they will.

Now, along comes professor Lieberman, not merely to use evolution to explain human behavior but to justify coercive left-wing social policy.

In other words, the left is not only progressive when it coerces citizens to act in ways the left deems appropriate but also science itself – through evolution – inexorably leads to government coercion on behalf of such policies.

Whereas until now, the Democratic left has attempted to persuade humanity that left-wing policies are inherently progressive, this Harvard professor has gone a huge step further. Left-wing policies are scientifically based. This is exactly how the Soviet communists defended their totalitarian system. Everything they advocated was “naoochni,” “scientific.”

To differ with the left is not only definitionally sexist, intolerant, xenophobic, homophobic, Islamophobic, racist and bigoted (SIXHIRB, as I have labeled it) – it is now against science itself.

Those who oppose Mayor Bloomberg’s law in the name of liberty are therefore missing the point. Not only does another left-wing god – health – demand government coercion, so does evolution itself. Those Americans who place liberty above other considerations and oppose Mayor Bloomberg’s proposal to ban large sodas might as well argue against the earth’s tilt because they don’t like winter.

That is the logical upshot of professor Lieberman’s position.

But there is an even more foolish and dangerous upshot to “we have evolved to need coercion.”

If we take this claim seriously and use evolution to guide social policy, little that is truly decent will survive. Is there anything less prescribed by evolution than, let us say, hospices? Professor Lieberman writes that humans have evolved into cooperating with one another. But he cannot deny that the basic evolutionary proposition is survival of the fittest. How, then, can an evolutionary perspective demand the expending of energy and resources to take care of those who are dying? And if evolution demands the survival of the species, wouldn’t evolution call for other “coercion” – against abortion, for example?

Which all proves that what the professor really means to say – and more and more college graduates will be taught – is this: “We have evolved to vote Democrat.”